Cilia and flagella are common organelles found on the surface of cells throughout the animal kingdom, in protozoa, and in some plants. Motile cilia and flagella play important roles in cell and fluid movement and are critical for normal patterning of the mouse left-right body axis. In addition, there are immotile cilia found on most epithelial and some nonepitheliat cells in the body. In contrast to the motile form, the function of immotile cilia is more obscure. In fact, the nearly ubiquitous nature of these immotile cilia has led some to speculate that they are vestigial. However, recent data suggest that defects in either form of cilia have devastating consequences. This is most evident by the systemic nature of the pathology seen in mice lacking cilia such as the Tg737 mutants. While cilia have been analyzed in lower eukaryotes, little is known about mammalian cilia assembly such as how the process is regulated, how the structural and signaling machinery are transported into the axoneme, or the mechanism by which signaling occurs through cilia. In this application, we begin to address some of these issues using the mouse and C. elegans as model systems. In the initial aim, we propose to evaluate whether ciliogenic mechanisms are conserved between these organisms, both at the level of protein function and transcriptional regulation of ciliogenic genes. The goals of the second aim are to utilize a database search of the C. elegans genome and a biochemical approach in mammalian sperm to identify novel components required for ciliogenesis. In the final aim, we will analyze the functional importance of these genes and determine how their corresponding proteins interact with other known proteins involved in the same process.Completion of the aims in this proposal will help elucidate a possible "universal mechanism (s)" driving eukaryotic ciliogenesis and will be an important advance required for future studies focused on the sensory roles of cilia and for identifying signaling machinery that concentrate in this specialized organelle. Understanding how cilia are built, are maintained, and signal will provide insights into the mechanism by which ciliary defects can have such devastating consequences to an organism. This includes such pathologies as cystic kidney disease, ductule hyperplasia of the pancreas and liver, hydrocephalus, blindness, sterility, abnormal skeletal patterning, and random determination of the left-right body axis.